Method of and means for measuring differences in time of propagation of wave fronts of different frequencies over a circuit



Oct. 8, 1929. HERMAN 1,730,368

' METHOD OF AND MEANS FoR MEASURING DIFFERENCES IN TIME OF PROPAGATION0F WAVE FRoNTs OF DIFFERENT FREQUENCIES ovER A CIRCUIT Original FiledDec. 1927 Steam (1) VAIAVIYI Y' All] INVENTOR. Jflrnmw ATTORNEY mas Oct.3, 1929 UNITED STATES PATENT OFFICE JOSEPH HERMAN, O! WESTIIEDD, NEWJERSEY, ASSIGNOB 'IO AMERICAN TELEPHONE AND rmamn COMPANY, A CORPORATIONOF NEW YORK METHOD 0! AND KEANE FOB IEASUBING DIFFERENCES IN TIME 01PROPAGATION OF WAVE. FBONTS 0! DIFFERENT FREQUENCIES OVER A CIRCUITApplication fi led December 2, 1927, Serial No. 237,802. RenewedDecember 7, 1928.

This invention relates to methods of and means for measuring thedifferences in the time of propagation of a wave front over a circuitwith currents of various frequencies.

- An instance wherein measurements of this character might be of valuewould be in the construction and design of new 'circuits,'and moreparticularly wit respect to the design I of networksto be utilized insuch circuits to discharging this condenser through an indieating means,such as a differential meter, adjusting the electrical constants of thechargin circuit of the condenser by means of a variabde resistance,repeating the above operations until the charge accumulated on thecondenser is equal to a known charge, and utilizing the values of theelectrical constants of the charging circuit when the charge accumulatedon the condenser is equal to a known charge to determine the interval oftime to be measured. In the arrangements and method of the presentinvention, current of any desired frequency Wlll be applied to or cutoff from one end of a circuit utilized as a standard for calibrationpurposes. This current will operate responsive means at the other end ofthe circuit. This responsive means will start the charging of thecondenser in the time measuring set, or in other words, will start themeasurin set in operation. Simultaneousl ,currento a ce rtain frequencywill be app ied to a circult n which it is desired to measuredifferences in dela wor s, differences in the time of propagation of awave front thereover at different frequencies. This current will operateresp lilnsive means at the end of said circuit. is

responsive means will be utilized to control at different frequencies,or in other the discharging of the condenser in the time measuring 'set,or in other words, to stop the other words, the two readings of themeasuring set may be subtracted to give the difference in delay at thetwo different frequencies over said second circuit. a

The invention may be more fully understood from the followingdescription together with the accompanying drawing in the figure ofwhich is illustrated a circuit diagram embodying a preferred form of theinvention.

In the drawing is shown a circuit 8 to one end of which is connected anoscillator 3. This oscillator may have a frequency F which may be anydesired frequency. Circuit 8 will include an amplifier-detector B, ameter M, and the winding of a relay D,. A circuit 7 is also provided. Itis over this circuit that it is desired to measure differences in timeof propagation of a Wave front at different frequencies, or inother'words, to measure differences in delay thereover at differentfrequencies. Accordingly, there will be connected to line 7 anoscillator 2. This oscillator may be adjusted to transmit any one of anumber of desired frequencies. Circuit 7 will include anamplifier-detector A, a meter M, and the winding of a relay D The timemeasuring set 3 is substantially similar to that illustrated in theaforementioned copending application filed in the name of J. Herman, andwill include a relay D for closing a charging circuit for the condenserC through the variable resistance R,. also include a relay D fordischarging the condensers C, and C through a differential meter M,. Adouble-pole switch SW is pro- It will vided for purposes to be pointedout hereinafter. The relay D normally controls a short circuit about thewinding of relay D and the relay D, controls a normally closed shortcircuit about the winding of relay D The circuits 7 and 8 include theresistance networks N and N respectively. Bridged across these networksare two circuits which may be closed upon the operation of the relay Dand which will be operated by the key K. The closing of these twocircuits will serve to simultaneously short-circuit the outputs ofoscillators 2 "and 3.

The operation of the arrangements is as follows: Normally, current willbe flowing from the oscillators 2 and 3 over the lines 7 and 8 and willhold the relays D and D on theirMcontacts. The oscillator 2 will nowhave its frequency adjusted to some desired value. The key K will now beclosed. This will operate relay 1),, which will close a short-circuitacross the outputs of both of the oscillators. Accordingly, relays D,and D will eventually-release. The release of relay D will open thenormally closed short-circuit about the winding of relay 1),. Relay ID,will operate and close a charging circuit for condenser C, through theresistance R 'Whenrelay l) releases, the normally closed short-circuitabout the winding of relay D will he opened and relay D will operate,thereby discharging condeflsers C and 0 through the differential meter MKe K will be opened and closed repeatedly an the resistance R, adjusteduntil the meter M will show no deflection. Thereading of resistance R,will then be noted. The frequency of oscillator 2 will now be changed toone of certain other frequencies which'it is desiredto measure. Theabove process will then be repeated for each frequency and the readingof R noted. The difference between one of these readings, chosen as areference, and the other readinga'will represent the difference in timeof propagation over the cir cuit 7 of wave fronts of the differentchosen frequencies. In case it should be'found that under certainconditions the relay 1), would operate before the, relay D,, the switchSW is provided with two positiops so that the connections to .theserelays may be interchanged. r

While the invention has been disclosed in certain specific arrangementswhich are deemed desirable, it is understood that it is capable ofembodiment in many and other widely varied forms without departin fromthe spirit of the invention as defined y the appended claims.

What is claimed is:

1. The combination of a time measuring set whereby a direct indicationmay be given of the time interval betweemthe operation of two responsivedevices, of two separate cir-' cuits each connected to one of saidresponsive devices, an oscillator of a definite frequency connected tothe first. of said circuits, an oscillator adapted to generate aplurality of desired frequencies connected to said second circuit, meansfor simultaneously controlling the application of current from saidoscillatorsto said circuits, means controlled by one of said responsivemeans for starting said measuring set in operation, and means con-'trolled by the other of said responsive means for stoppingthe operationof said measuring set.

2. The method of measuring difierencein delay over a circuit withcurrents of different frequencies, which comprises controlling theapplication of current of a definite frequency over a circuit to beutilized for comparative purposes, simultaneously controlling theapplication of current offone of a plurality of desired frequencies overthe circuit in question, measuring the difference in delay be tween thecurrent of known frequency and the current of desired frequency over theseparate circuits, repeating the measurement in turn with currents ofother of the plurality of desired frequencies over the circuit inquestion, and comparing said measurements. v

Intestimony whereof, I have signed my name to this specification this1st day ofDecember1927.

JOSEPH HERMAN.

